The prolonged exposure to UV radiation, such as from the sun, can lead to the formation of light dermatoses and erythemas, as well as increase the risk of skin cancers, such as melanoma, and accelerate skin aging, such as loss of skin elasticity and wrinkling.
Numerous sunscreen compounds are commercially available with varying ability to shield the body from ultraviolet light. For example, the various sunscreen compounds may absorb or block ultraviolet different portions of the ultraviolet spectrum, such as ultraviolet light having wavelengths in both the UV-A range (from about 320 to 400 nm) and the UV-B range (from about 280 to about 320 nm), or some combination of both of these spectral ranges.
It has been suggested to use sunscreen molecules having high molecular weights in order to reduce the penetration of the sunscreen molecule through the epidermis. However, only a limited number of options for high molecular weight sunscreen compounds exist. As such, applicants have recognized it would desirable to have new polymeric sunscreen compounds (ultraviolet radiation-absorbing polymers) that are suitable for inclusion in topical sunscreen compositions. It would also be desirable for the UV-absorbing polymers to, when formulated, provide compositions that are capable of imparting one or more of good spreadability, low gloss, non-greasy texture, waterproofing, high SPF, high PFA, and favorable PFA/SPF ratio (broad spectrum protection). Applicants have discovered that UV-absorbing polymers comprising a first pendant group that comprises a UV-absorbing moiety and a second pendant group that comprises at least one siloxane linkage and/or an intermediate length carbon chain provide particular advantages, whether used alone or blended with other UV-absorbing polymers.